JPH025533B2 - - Google Patents

Description

Claim 1 A camshaft remanufacturing method that includes building up the worn surface with steel, applying heat treatment to the camshaft 1 to relieve stress, applying heat treatment to remove strain to increase strength, and grinding. The build-up is limited only to the worn surface of the cam 2 exceeding the allowable limit, and after the repair, a layer slightly exceeding the specified size is welded, and the camshaft 1 is subjected to stress relief heat treatment and After the heat treatment for strain relief, all of the overlaid cams 2 and 3 and the intact cam are ground to repair dimensions, and then the camshaft 1 is nitrided for extra strength, and then strain relief is applied once again. A method for regenerating a camshaft, characterized in that:

2. Method according to claim 1, characterized in that the steel electrode rod is used for overlaying the cast iron camshaft 1 in areas which have been locally worn below an acceptable limit.

3 Stress relief heat treatment of cast iron camshaft 1 is performed at 600~
A method according to claim 1, characterized in that the treatment is carried out at 610° for 3 to 3.5 hours.

〔Technical field〕

TECHNICAL FIELD The present invention relates to the repair of machines, and more particularly to a method for recycling camshafts.

[Background technology]

During operation, wear is limited to some of the machine components due to the isolated loading surfaces. Thus, for example, the camshaft of a motor vehicle valve system is subject to local wear on the cam, while the boss remains virtually unchanged.

It is known to recycle worn camshafts, which consists in sanding the remaining amount comparable to the amount of wear on the cam, applying a circumferential strip to the cam and sanding them (see, Patent of Japan No.
5247094;series 4/1:Bulletin 77/383;
1977).

Despite the existence of labor consumption, this method cannot guarantee the reliability of the repaired object.

It is also known to recycle the valve gear of internal combustion engines, which consists in machining the worn surface of the camshaft to repair dimensions and inserting it into the inner diameter of the camshaft bearing (see "Remont Dvigatelei").
avtomobilei GAZ”Shneider GKGorky
Publishers, 1955, pp. 236-237).

However, this method is also not suitable for repairing heavily worn cams, and through machining,
Because the wear-resistant layer is removed by grinding, the reliability of the remanufactured cam cannot be guaranteed, and the fabrication and insertion fit are labor-intensive.

Furthermore, it is also known to recycle camshafts by means of fire spraying (see,
“Gazotermicheskoe napylenie iznoshennykh
detaili mekhanizma gazoraspredelenia
dvigatelei avtomobilei VAZ”，BI
Maximovich et al., “Avtomobilnaya
Promyshlennort”magazine, No. 7, 1983).

This process involves resizing the worn cam and using a spray gun to apply a 2.5-3.0 mm weld of self-fusing alloy powder to the cam in the molten state. The second and fourth bearing bosses are updated in a similar manner by welding a layer of only 0.3-0.4 mm thick. The materials needed to update the 8 cams and 2 bearing bosses are:
It is 120-150gr, and the working time is 10-15 minutes. After being updated and cooled to room temperature, the camshaft is straightened on a strain relief machine using the center bearing boss for a surface check. Updated cams and bearing bosses can be used on profile grinders or circular grinders
It is ground with

Camshaft repairs on this line are expensive. It is expensive because it requires expensive alloy powder. Surface conditioning, modification and grinding of the bearing bosses is also difficult and labor consuming due to the use of alloy powder. Additional circular grinders are also required to successfully handle the job. This method cannot be applied to modify the first, third and fifth bearing bosses.

As a technique, it is known to modify worn surfaces of steel camshafts with steel electrode rods that are post-treated by hardening and grinding (see "Remont traktorov", Pogorely IPet al.,
OTIZ Selkhos State Publishers, 1960, pp.154
−155). The cams were roughened before being modified and
To remove camshaft distortion caused by hardening, the boss is ground to repair size. At the same time, the boss is repaired, but in this case special components must be provided. This method is therefore both labor and material consuming.

In addition, as a technology, submerged arc welding (submerged arc welding) using steel electrode rods is also available.
It is also known how to repair metal parts by welding (see, VANalivkin
“Tsentralizovannoe vosstanovlenie detalie
avtomaticheskoi naplavkoi i svarkoi”
Privolshskoe Publishers, Saratov, 1965,
pp.106-107).

This process is performed as follows.

As soon as the surface is cleaned of dirt remaining after operation, each component is free from defects (chips, dents, dents, etc.) that affect its dimensions, shape and mechanical properties.
cracks, signs of wear).

Surface preparation then involves mounting each component with fixtures that facilitate straightening, repairing surface treatment standards, and modification.

The worn surface is then modified either cold or as soon as it is heated.

Subsequently, first a heat treatment is applied to reduce the distortions caused during modification. Any processing required is annealing or conditioning.

Next, change the weld layer from rough to finish,
Begin machining, including milling, planing, and drilling. Strain relief is sometimes required after modification or often after heat treatment.

The machining is followed by other heat treatments consisting of tempering, annealing, and curing.

Finally, the roughness is removed by precision grinding, precision drilling, and similar processing. Also included are various fine finishes such as honing and lapping.

The sequence of steps described above generally applies to the repair of steel elements, preferably to components in the form of rotating bodies.

Any wear on any surface can be repaired using submerged arc welding. If the wear is low, in order to form a deposited metal layer of the required thickness,
Some metal is removed from the worn surface. A commonly used heat treatment to increase strength is induction hardening. Alloy steels are commonly used to achieve the desired strength of the weld metal.

However, the materials used are expensive and
Complex machining involves labor consumption, and the wear resistance of the modified surface is low.

[Disclosure of the invention]

The main object of the present invention is to provide a camshaft remanufacturing method that ensures that the quality of the remanufactured product is at a new level by using improved technology.

This purpose is to improve the build-up in the camshaft remanufacturing method of the present invention, which includes build-up of the worn surface with steel, heat treatment of the camshaft to relieve stress, heat treatment to remove strain to increase strength, and grinding. , limited only to cam surfaces that are worn beyond acceptable limits,
After repair, a layer slightly exceeding the specified dimensions was welded, and the fully built-up cam was subjected to stress relief heat treatment and strain relief treatment, and then ground to the repair dimensions. The camshaft is then nitrided to give it extra strength.
This is achieved by removing the distortion again.

Steel electrode rods are advantageously used for local build-up of cast iron camshafts.

In addition, stress relief heat treatment for cast iron camshafts is performed at 600~
Conveniently, the treatment is carried out at 610°C for 3 to 3.5 hours.

The disclosed method of camshaft refurbishment provides minimal consumption of material and a failure-free bond between the cast iron and steel surfaces of the cam.

The nitriding process uniformizes the strength properties of the cast iron and steel surfaces of the cam. It also increases the strength of the bearing bosses at the same time as their strengthening treatment.

The effort required to remanufacture a camshaft using the disclosed method is one half of the effort required to manufacture a new camshaft.

The disclosed method also uses recycled metals (secondary metals).
Create uses for metal).

[Brief explanation of drawings]

A preferred embodiment of the invention will be described by way of example with reference to the accompanying drawings, in which: FIG. 1 shows a modified camshaft; FIG. 2 shows a cam repaired according to the invention; FIG. 3 shows a cam ground according to the invention; FIG. 4 shows the contact area between the cast iron surface of the cam with a carbonitrided layer according to the invention and the welded steel surface. It shows.

[Best mode for carrying out the invention]

For example, let us devise a means by which a cast iron camshaft (Fig. 1) may be repaired.

After a period of operation, the five cams 2 have worn below the permissible limit by an amount of C ₁ -C ₂ /2 (Fig. 2), and the three camshafts 3 have worn below the permissible limit by an amount of C ₁ -C ₂ /2 (Fig. 2). Showing less wear. where C ₁ is the diameter of the basic circle of the new cam, and C ₂ is the diameter of the basic circle of the cam of repair dimensions.

The wear for all bosses 4 (FIG. 1) is uniform due to the conditions of camshaft operation and does not exceed 0.01 mm. The maximum wear on the boss 4 does not exceed 0.03 mm for this type of camshaft.

After cleaning the camshaft, the centering surfaces 5 and 6 are readjusted on a lathe (not shown).

The five cams 2 are then assembled using steel electrode rods (not shown) under a gas shield created by semi-automatic built-up equipment (C ₁ -C ₂ /2). (Fig. 2) more is built up in the area of wear, ie between points 7 and 8. Having build-up only in the wear area on cam 2 minimizes the need for alloy additives. In this case, the heat input is also at a minimum such that the ductility of the cast iron camshaft 1 (FIG. 1) is not affected. The slightly worn cam 3 is not built up at all. This saves more on alloy additives.

The removal of the internal stresses of the camshaft that are generally generated during manufacturing (for example, the stress of induction hardening), fatigue during use, stress due to build-up of the cam 2, etc. is achieved by using the protective gas of the shaft furnace. 3~ at 600℃ in atmosphere
Heat treated for 3.5 hours and cooled. This stress relief condition prevents cracking at the interface between the steel and cast iron parts of cam 2 and maintains the ductility of camshaft 1 unchanged so that the camshaft is strain relieved to exact dimensional accuracy. do.

The deformation is removed on a strain relief press.

After straightening, cams 2 and 3 are ground to repair dimension C ₂ (Figures 2 and 3) on a semi-automatic profile grinder.
During the grinding operation, the height H of the cam repair dimension C ₂ (third
(Fig.) and its height should be taken care of so as not to reduce the engine power.
And the design of the valve device must be chosen so that the special valve device is made identical to the original valve.

The strain-removed camshaft is nitrided in a mixture of ammonia gas and Exogas using a shaft furnace.

The carbonitrided layer 9 formed on the cam 2 (FIG. 2) surface during the nitriding process provides identical strength properties to the cast iron surface 10 and the steel surface 11.

The radial build-up of the nitrided surface resulting from the introduction of carbon and nitrogen allows the boss to be repaired to the dimensions depicted in the drawings.

The camshaft (first
The deformation in Figure) is removed with a strain relief press.

The camshaft remanufactured by the disclosed invention is
Fully meets the requirements specified for new camshafts and has a service life of at least 125000Km.

The effort required to remanufacture a camshaft by the disclosed method is one half of the effort required to fabricate a new camshaft on similar equipment.

[Industrial applicability]

The present invention finds application in retrofit build-ups of steel and cast iron camshafts for spark ignition diesel engines.